Field of the Invention
The present invention relates to an electrophotographic photosensitive member, and a process cartridge and an electrophotographic apparatus each including the electrophotographic photosensitive member.
Description of the Related Art
An electrophotographic photosensitive member containing an organic photoconductive substance (charge generating substance) has been mainly used as an electrophotographic photosensitive member to be mounted to a process cartridge or an electrophotographic apparatus. In recent years, there has been a growing requirement for the quality of an electrophotographic image, and hence an improvement has been attempted to correspond to various technical problems in the electrophotographic photosensitive member. For example, the following method has been known as a method of solving technical problems caused by the inflow of a hole from a support, such as a black spot and ground fogging. An undercoat layer is arranged between the support and a photosensitive layer to suppress the inflow of the hole from the support by virtue of its blocking function. On the other hand, when the resistance of the undercoat layer is excessively high, it becomes difficult to transport an electron generated in the photosensitive layer to the support, and hence a positive ghost (phenomenon in which during the formation of one image, when a portion irradiated with light becomes a halftone image in the next rotation of the electrophotographic photosensitive member, the density of only the portion irradiated with light becomes high) occurs in some cases.
A method involving controlling the resistance through the use of a metal oxide as an electro-conductive agent has been proposed as one method of suppressing the positive ghost, but the method reduces the blocking function of the undercoat layer itself.
In view of the foregoing, an investigation has been made on a method of suppressing the positive ghost even when the metal oxide is not incorporated or is incorporated but its amount is small (the content of the metal oxide in the undercoat layer is 10 mass % or less). Specifically, a technology involving incorporating an electron transporting substance into the undercoat layer has been known for improving the electron transporting ability of the undercoat layer (Japanese Patent Application Laid-Open No. 2001-83726 and Japanese Patent Application Laid-Open No. 2003-345044).
In each of Japanese Patent Application Laid-Open No. 2001-83726 and Japanese Patent Application Laid-Open No. 2003-345044, there is a disclosure of a method involving incorporating the electron transporting substance, such as a fluorenone compound derivative or an imide compound derivative, into the undercoat layer.